Do a search in the Roofing Business section on supplementing. I posted 2 rather extensive threads, specifically on supplementing, a few years ago.
Below are images of a supplement I sent in recently. Reasonably simple actually. Describe the supplemental item you’re requesting. Why you’re requesting it or why it is justified. And a picture to support your statements. In general, if you don’t have a picture, don’t bother. Pictures are dollars.
I also highly recommend Snagit software. You can crop out screen shots and put in the annotations you see easily. Most valuable supplementing tool I use. Around $50. I think Techsmith is the Parent company.